<form class="form-inline" role="search" method="get" id="searchform" action="<?php echo home_url( '/' ); ?>">
    <input type="text" class="form-control" id="s" name="s" value="<? the_search_query();?>" placeholder="网站检索">
    <button class="btn btn-default" type="submit" id="searchsubmit"><span class="glyphicon glyphicon-search" aria-hidden="true"></span></button>
</form>